The invention relates to carrier particles for delivery of a drug and a process for preparation of carrier particles.
Pharmaceutical delivery systems for hydrophobic drugs have conventionally involved formulating the drug with a carrier particle such as a liposome or an emulsion. Due in part to the large particle size and foreign shape of the particle, the body quickly recognizes these conventional particles as foreign and rapidly clears them from the plasma.
Rapid clearance of a drug reduces drug efficacy by limiting the availability of the drug to the target tissues. Drug toxicity in the clearance tissues, particularly renal toxicity, may result from the high drug concentration caused by this rapid clearance of hydrophobic drugs delivered by conventional carrier particles.
Liposomes consist of one or more concentric lipid bilayers separated by aqueous compartments, and having and aqueous core compartment. The concentric lipid bilayers are usually comprised of phospholipid bilayers. Liposomes can be used to deliver hydrophobic drugs by incorporation of the drug into the lipid bilayer, or may be used to deliver hydrophilic drugs by encapsulation of the drug in the aqueous compartments or core space. Depending on the number of concentric bilayers, and the quantity of substance encapsulated therein, liposomes may range in size from small unilamellar vesicles of about 50 nm in diameter to large multilamellar vesicles of up to 10 xcexcm in diameter. Liposomes for delivery of a hydrophobic drug are disclosed, for example, in U.S. Pat. No. 5,795,587 (Gao et al.; Aug. 18, 1998).
Liposomes have the drawback that the amount of drug contained in each particle is limited. Unilamellar vesicles have a particularly low hydrophobic drug loading capacity, and are more effectively used for delivery of hydrophilic drugs in the particle core. Multilamellar liposomes are more suitable for hydrophobic drug incorporation, but due in part to the large particle size and foreign shape, the body quickly recognizes these conventional particles as foreign and rapidly clears them from the plasma.
Emulsions are heterogeneous systems of lipid particles dispersed in an hydrophilic or aqueous medium. Hydrophobic drugs may be incorporated into the lipophilic phase of the emulsion. Emulsion particles are often large in size and these particles frequently exceed 1 xcexcm in diameter. To achieve smaller sized particles and to stabilize particles against coalescence, detergents or surfactants may be incorporated into an emulsions. Such stabilizers may disadvantageously act as hemolytic agents, thereby solubilizing membranes when injected into the body. Amphipathic lipids are those lipids which have both a hydrophobic and a hydrophilic moiety on the same molecule. An example of an amphipathic lipid is a phospholipid. Amphipathic lipids have been used to stabilize lipophilic drug emulsions.
Carrier particles referred to as xe2x80x9cemulosomesxe2x80x9d, having features intermediate between liposomes and emulsions, are described in U.S. Pat. No. 5,576,016. Emulosomes have a lipid core containing, in combination with the hydrophobic drug of interest, a triglyceride, wax or ester which is in a solid or liquid crystalline phase at 25xc2x0 C. The emulosome core is surrounded by an outer phospholipid monolayer or bilayer containing a surfactant. Emulosome particles are smaller than conventional emulsion particles, and range in size from 10 to 250 nm in diameter, having an average diameter from about 50 to 150 nm. However, such a heterogeneous particle size distribution may be disadvantageous, since metabolism of the particles may vary according to size.
Following intravenous administration of hydrophobic drugs in conventional liposome particles, transfer of the drug from the initial carrier to plasma lipoproteins occurs. Association of amphotericin B with native serum low-density lipoprotein (LDL) was shown to correlate with renal toxicity of the drug, possibly through LDL-receptor mediated drug uptake by kidney cells (J. Pharm. Tox. Meth. 1996;36:1-11). Additionally, it has been shown that the more rapidly or completely amphotericin B is transferred from a liposomal particle to native serum high-density lipoprotein (HDL) in vivo, the less renal toxicity it displays (Antimicrob. Agents Chemother. 1994;38:223-227). Thus, HDL-associated amphotericin B exhibits less renal toxicity than LDL-associated amphotericin B.
U.S. Pat. No. 4,868,158 (Masquelier et al.; Sep. 19, 1989) teaches a method for the production of a complex containing reconstituted LDL which carries a lipophilic drug. Lyophilized LDL was mixed with the drug, a solvent, and a protective agent to stabilize the resulting complex, for example, a sugar alcohol, or a mono-, di- or poly-saccharide. The solvent was removed and the LDL-drug complex was then reconstituted. This LDL-drug complex is intended in part to target the drug to cells having high levels of LDL receptors.
U.S. Pat. No. 5,324,821 (Favre et al.; Jun. 28, 1994) discloses a method of incorporating a lipophilic drug into a lipoprotein complex, preferably containing LDL. The method involves preparing an emulsion, adding the lipophilic drug, the lipoprotein and a lipid transfer protein, and incubating the mixture. Those lipoproteins complexed with the drug may then be isolated from the incubation mixture and used for pharmaceutical purposes.
Methods for preparing reconstituted HDL particles are known. For example, U.S. Pat. No. 5,652,339 (Lerch et al.; Jul. 29, 1997) discloses a method of producing reconstituted HDL particles from apolipoprotein A-I and phosphatidyl choline. However, this document does not teach the use of reconstituted HDL for hydrophobic drug delivery.
U.S. Pat. No. 5,128,318 (Levine et al.; Jul. 7, 1992) describes a method for reconstituting HDL-like particles using a detergent dialysis emulsification technique. Sodium cholate, a bile acid, is used as a detergent to effect emulsification. The resulting HDL-containing particles are disc-shaped, unlike native HDL. The particles are intended for use in removing excess lipid-soluble material, such as endotoxin, from a subject. In use in vivo, lipid-soluble material moves into the centre of the disc-shaped carrier. This document does not describe the preparation of a drug carrier complex or any methodology for associating a drug with the particle.
The present invention provides carrier particles which are small in size and not easily recognized as foreign by the body for drug delivery of hydrophobic, amphipathic, or cationic lipophilic drugs. The present invention further provides a process for preparing carrier particles comprising drugs. It is an object of the invention to circumvent drawbacks in hydrophobic drug delivery described in the prior art.
The above object is met by the combinations of features of the main claims, the sub-claims disclose further advantageous embodiments of the invention.
The invention relates to carrier particles for delivery of a drug and a process for preparation of carrier particles.
According to the invention, there is provided carrier particles for a drug and a method for the preparation of a carrier particles and a drug. The carrier particle comprises at least one HDL apolipoprotein, preferably apolipoprotein A-I (apo A-I) or apolipoprotein A-II (apo A-II), at least one amphipathic lipid, and at least one drug selected from the group consisting of hydrophobic drug, an amphipathic drug, and a cationic hydrophilic drug. The carrier particle has a diameter of from about 5 nm to about 20 nm.
The invention additionally provides a composition for delivery of a hydrophobic, amphipathic or cationic hydrophilic drug which comprises carrier particles, as described above, in combination with a pharmaceutically acceptable medium in which the carrier particles are dissolved or suspended. The carrier particle may comprise a lipid-soluble component, selected from the group consisting of:
i) a fatty acid having from 8 to 24 carbons, said fatty acid either saturated or containing one or more unsaturated bonds;
ii) an ester of said fatty acid;
iii) mono-, di-, and tri-glycerides of said fatty acid;
iv) cholesterol, or an ester thereof;
v) an antioxidant;
vi) a steroid hormone;
vii) a small hydrophobic peptide,
viii) vitamin A, D, E, or K; and
ix) xcex2-carotene.
According to the invention, a method is provided for delivery of a hydrophobic, amphipathic or cationic hydrophilic drug to a mammalian subject comprising administering to the subject an effective amount of the above-described carrier particle or composition.
Thus, in one aspect, the invention provides a process for preparing a synthetic HDL spherical particle comprising at least one HDL apolipoprotein, at least one amphipathic lipid, and at least one hydrophobic active agent, said process consisting essentially of the steps of: (a) admixing at least one amphipathic lipid with at least one hydrophobic active agent in a solvent, said at least one hydrophobic active agent being selected from the group consisting of a hydrophobic drug, an amphipathic drug, and a lipid-soluble component; (b) removing said solvent to produce a dried mixture; (c) hydrating said dried mixture in an aqueous buffer to produce an aqueous mixture, said aqueous buffer being essentially free of detergent; (d) adding at least one HDL apolipoprotein to said aqueous mixture; and (e) vigorously mixing by sonication, trituration, or homogenization said HDL apolipoprotein and said aqueous mixture to form said synthetic HDL spherical particle.
In a further aspect, the invention provides a synthetic HDL spherical particle made by the process described herein, said synthetic HDL spherical particle comprising: at least one HDL apolipoprotein, at least one amphipathic lipid, and at least one hydrophobic active agent, said hydrophobic active agent being selected from the group consisting of a hydrophobic drug, an amphipathic drug, and a lipid-soluble component, and said synthetic HDL spherical particle being generally spherical and having a diameter of from about 5 nm to about 20 nm.
In a further aspect, the invention provides a composition comprising: (a) a spherical carrier particle comprising at least one HDL apolipoprotein and at least one amphipathic lipid; and (b) a hydrophobic active agent entirely disposed within the spherical carrier particle of (a) to form a synthetic HDL spherical particle having a diameter of from about 5 nm to 20 nm, said hydrophobic active agent being selected from the group consisting of a hydrophobic drug, an amphipathic drug, and a lipid-soluble component.
Further, according to the invention, there is provided a process for preparing carrier particles for a hydrophobic, amphipathic, or cationic hydrophilic drug comprising the steps of: (a) mixing an amphipathic lipid with at least one drug in a solvent; (b) removing the solvent to produce a dried mixture; (c) hydrating the dried mixture in an aqueous buffer to produce an aqueous mixture; (d) adding at least one HDL apolipoprotein to the aqueous mixture; and (e) vigorously mixing the apolipoprotein with the aqueous mixture to form carrier particles. The particles formed according to this method contain the drug and have a diameter of from about 5 nm to about 20 nm.
Without being bound by theory, the apolipoprotein component of the particle helps to disguise the particle so that the body does not immediately recognize it as foreign, but may allow the body to perceive it as native HDL. The small size and the approximately spherical shape allow the particle to exhibit similar physicochemical properties to native HDL. Because the carrier particles are not recognized as foreign, the systemic circulation of the drug increases, thus increasing the likelihood of drug delivery to the target tissues. Additionally, the clearance rate of the drug decreases, thereby reducing the likelihood of toxic effects of the drug on clearance tissues since accumulation of the drug in clearance tissues is reduced, especially for hydrophobic drugs. Furthermore, specific organs may be targeted by using carrier particles as described herein, due to target cells comprising high levels of specific receptors, for example but not limited to apoA-I receptors.
This summary of the invention does not necessarily describe all necessary features of the invention but that the invention may also reside in a sub-combination of the described features.